No, that is not a de-aged Winona Ryder in Stranger Things Season 5. And yes, you have seen the actress before. You have actually seen her in a recent episode of Chicago Fire.
In Episode 4 of the final season of the series, we see Max exploring Vecna’s memories of his time at Hawkins High School during the 1950s. That includes a young Joyce Maldonado, who is seen handing out flyers for a production of the musical “Oklahoma!”.
You might have thought that was just CGI, a de-aged version of Ryder. We grew up with her on our screens, so we are very familiar with what young Winona Ryder looked like, after all. But no, this Ryder look-alike is actually actress Birdy, who you have seen before! She played Haley in the Season 13 finale of Chicago Fire.
The actress herself confirmed it on Instagram.